SACRAMENTO, Calif. (AP) - The U.S. Department of Agriculture is issuing a public health alert for raw chicken packaged at three Foster Farms facilities in California after 278 people have fallen ill. The USDA says that strains of Salmonella Heidelberg are associated with chicken distributed to retail outlets in California, Oregon and Washington state. The Salmonella outbreak has spread to 18 states, though most of the illnesses have been reported in California. A spokesman for Foster Farms says no recall is in effect and that the infections were caused by eating undercooked or improperly handled chicken. The USDA has not directly linked the outbreak of illnesses to a specific product or production period. The USDA mark on suspect packages would read: P6137, P6137A and P7632. Cooking chicken to 165-degrees kills the Salmonella bacteria.